Mechanically commutated motors utilize a commutator and brushes to transfer electric power to a rotating element of the motor, typically an armature. The armature has a shaft on which a commutator is affixed. Generally, the brushes transfer power from a DC or AC power source to the commutator causing the armature to rotate. Each brush is supported adjacent the commutator so that it contacts the commutator. In some cases, each brush is at least partially enclosed in a brush box that is used to connect the brush to the power source and to support the brush adjacent the commutator. One type of brush box is a one piece device constructed of electrically conductive material, such as copper or brass. The brush box may be mounted by being attached to an end cap affixed to one end of the motor housing. The end cap also typically provides a bearing support that supports a bearing in which the armature shaft is journaled. In this regard, the one piece brush box is often secured to the end cap at only one point.
The one piece design of brush boxes often does not securely retain the brush during motor operation, thereby allowing the brush to move, which can cause excessive wear on the brush and the commutator. Additionally, securing the brush box at only one point also allows the brush to move causing excessive wear. Also, brush boxes with only one connection point may more easily separate from the element of the motor on which they are mounted causing the motor to fail. The excessive wear, or possible failure, create added costs in parts, labor, and maintenance.
Further yet, end caps are not generally constructed of materials having high temperature properties and thus are not well suited to withstand excessive heat generated by the interaction between the commutator and the brushes during prolonged operation of the motor. Therefore, prolonged or repeated use at high current loadings over the long periods of time could cause an end cap on which a brush box is mounted to char, deform, or melt, thereby causing the motor to fail and add further parts, labor, and maintenance costs.